Leukostasis in vessels in CLL patients in vivo is very difficult to identify, since there are no clinical and radiological manifestations of this complication, it is noted that leukostasis develops less frequently in patients with CLL than with acute leukemia and chronic myeloid leukemia. At the same time, impaired rheological indices of blood and pulmonary circulation is an important link in the pathogenesis of CLL. A decrease in pulmonary circulation is found in 97% of patients with CLL. The risk of developing leukostasis in the vessels of the lungs appears with an increase in the number of blood leukocytes above 50 × 109 / l, and with an increase of more than 200 × 109 / l, leukostasis almost always develops.

Pneumonia in CLL deserves special attention, because they are the dominant complication (up to 75%), playing a major role in the outcome of the disease. In a half of patients with CLL, a history of frequent pneumonia can be detected even before the onset of the disease. On the fact that pneumonia is the most common cause of mortality in patients with CLL, many authors point out. The occurrence of pneumonia is directly dependent on the presence of concomitant or previous pulmonary infectious process, i.e. leukemic infiltration of the lungs and bronchi. The pathogenesis of pneumonia may be different. Lymphoid infiltration of the bronchi can lead to their infection, the development of pneumonia and the death of a patient with CLL. The development of pneumonia in CLL can contribute to microcirculation disorders due to high leukocytosis.

Due to the development of lymphatic leukocytosis in B-CLL, these patients have varying degrees of severity of neutropenia. Belongs to pneumonia, occurring on the background of neutropenia, among the most severe, which often have a poor prognosis. They are characterized by complications: abscess formation, prolonged course, severe dysbiosis, sepsis. When the number of granulocytes in peripheral blood is <0.5 × 109 / l, the risk of developing infectious complications is higher than that of patients with a number of granulocytes> 1.0 × 109 / l, the risk of infectious complications is especially high with a level of granulocytes <0.1 × 109 / l [50]. With neutrophil count> 0.5 × 109 / l, a positive response to antibiotic treatment is observed in 90% of patients, and mortality is 7%, while with neutrophil count <0.5 × 109 / l – 60 and 20% respectively [50, 309, 355]. According to the WHO classification, there are 4 degrees of neutropenia. Especially dangerous is grade IV neutropenia (neutrophils less than 500 in 1 µl of blood), but patients with neutrophil count less than 100 in 1 µl are also isolated. The latter subgroup is the most threatened from the point of view of the development of fast-flowing gram-negative infection.

Of considerable interest is the work on the clinical and morphological features of pneumonia that occur in oncohematological patients against the background of myelodepression and neutropenia. The authors showed that for a microscopic picture of pneumonia on the background of myelodepression, there is a characteristic lack of manifestations of an inflammatory cell reaction in the lung tissue due to a sharp decrease in neutrophilic granulocytes in the circulating blood. In the lung tissue, exudation prevails, extending along the interalveolar passages without forming an inflammatory wall, limited only by anatomical structures (interlobar pleura). In this regard, in the specified period lobar pneumonia is characteristic.

Leukemia cells, infiltrating the interalveolar septa, as a rule, do not enter the lumen of the alveoli. In the respiratory region of the lung tissue, desquamation of the alveolar epithelium is observed, which further enhances exudation. In the absence of neutrophils, the alveolar macrophages play the main role in the clearance of alveoli from pathological contents. Therefore, the authors believe that the diagnosis of pneumonia in oncohematological patients is eligible even in cases of detecting serous contents in the alveoli in combination with the growth of fungal mycelium or microbial colonies.